Perianth development in the basal monocot Triglochin maritima (Juncaginaceae)

Matyas Buzgo, Douglas E. Soltis, Pamela S. Soltis, Sangtae Kim, Hong Ma, Bernard A. Hauser, Jim Leebens-Mack, Bo Johansen

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    Abstract

    Basal monocots exhibit considerable variation in inflorescence and floral structure. In some cases,

    such as Triglochin maritima, it is not clear whether the lateral and terminal structures of the inflorescence

    are flowers or pseudanthia, or where the limits between flowers and inflorescence lie. To address

    these questions, morphological studies were carried out, and the results show that in T. maritima both

    terminal and lateral structures are flowers, not pseudanthia. The terminal flower of T. maritima develops

    from the apical inflorescence meristem, suggesting that the apical meristem identity changes

    from ‘‘inflorescence'' to ‘‘flower'' during inflorescence development. In addition, distal flowers of T.

    maritima are reduced, and there is no distinct flower-subtending bract; instead, the perianth develops

    are reduced, and there is no distinct flower-subtending bract; instead, the perianth develops

    unidirectionally, resulting in an abaxial-median bract-like tepal and bilaterally symmetrical flowers,

    similar to those of other basal monocots, such as Aponogeton and Acorus. It is possible that the leaf

    primordium changes its positional homology from ‘‘flower-subtending bract'' to ‘‘tepal.'' Therefore,

    in some basal angiosperms with abbreviated development of lateral flowers the demarcation of the

    flower vs. the inflorescence is ontogenetically ambiguous. In situ hybridization experiments show that

    a putative ortholog of the B-class gene APETALA3/DEFICIENS is expressed in developing stamens

    and carpels, and may also be expressed in the shoot axis of the very young inflorescence. This

    expression pattern seems to be consistent with the gradual transition between inflorescence and flower

    that was observed morphologically.

    OriginalsprogEngelsk
    TidsskriftAliso
    Udgave nummer22
    Sider (fra-til)107-125
    ISSN0065-6275
    StatusUdgivet - 2006

    Bibliografisk note

    Key words: APETALA3, basal angiosperms, fading borders, gene expression pattern, Juncaginaceae,
    MADS-box gene, monocots, organ identity, Triglochin.

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